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Goodwill and Intangible Assets - Additional Information (Details) $ in Millions | 3 Months Ended
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Dec. 31, 2020 USD ($) acquisition
Goodwill and Intangible Assets Disclosure [Abstract] |
Number of asset acquisitions | acquisition | 2
Increase in intangible assets, assets acquired | $ | $ 318

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- Definition Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16265-109275 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration

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- Definition Number of Asset Acquisitions + References No definition available. + Details
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Namespace Prefix: | wmg_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration